Within the last decade salmon aquaculture in Tasmania has moved from holding “an enviable social license” to the most contested issue in the state. We have analysed the reasons behind this damaging transition and developed a social influence model that represents exchange of opinions between individuals and the influence of mass media. The model provides (i) accurate and detailed hindcasts of the tipping point from population consensus to high conflict discourse; and (ii) a platform for quantitative evaluation of communication strategies aimed at reducing this conflict. We found that advocacy is likely to be ineffective and often counterproductive in the salmon debate; whereas use of neutral highly credible spokespersons was highly effective when messaging was regularly targeted across a large proportion of the population. When the messaging was targeted too narrowly or too infrequently, any positive effect was largely offset by ongoing exchange of misinformation within the population.